Abstract The objective of this study was to evaluate different combinations one-carbon metabolites [OCM: rumen-protected methionine (RPM), choline (RPC), folate (FA), vitamin B12 (B12)] on pancreatic and jejunal carbohydrase activity at d 14 the estrous cycle in beef heifers. Thirty Angus heifers were fed a high-roughage diet assigned treatments: 0% RPM + 0 g/d RPC saline injection (0XNEG), 0.0...